### Description
<!-- Describe your changes. -->
Update various test projects to .net8 from EOL frameworks.
Replace the Xamarin based Android and iOS test projects with a MAUI
based project that uses .net 8.
Add new CoreML flags to C# bindings
### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->
Remove usage of EOL frameworks.
### Description
1. rename OrtValue.FillStringTensorElement to StringTensorSetElementAt .
To the API user I think we're conceptually setting the string at an
offset in the tensor with is roughly equivalent to `List<string> list
... list[index] = "value"`.
2. While working on new inference examples, I noticed that I am still
inclined to use `DenseTensor` for N-D indexing. Added `GetStrides()` and
`GetIndex()` from strides for long dims, so the user can obtain strides
and translate N-D indices into a flat index to operate directly on the
native `OrtValue` buffers. Expose these functions to the user.
3. Make sure we generate docs for C# public static functions.
### Description
1) Added Sequence And Maps convenience APIs to create input Sequences
and Maps
and also visit the outputs.
2) Address OrtValue design issue when the values are created on top of
the
managed memory and the ortValues are used for sequence and maps
creation.
We should retain the original managed instances that keep the memory
pinned.
We opt to keep track of those and dispose of them within an instance of
OrtValue
that represents a Map or a Sequence.
3) Set `LangVersion` to default per [MS Versioning
Docs.](https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/configure-language-version)
### Motivation and Context
1) When writing code examples, use of Map and Sequences API proved to be
cumbersome.
2) It is a BUG, that we should address, as the managed memory can move
by the GC and lead to
intermittent crashes.
3) Make use of the most feature of the C#.
### Description
Introduce `Float16/BFloat16` support for C# and C++ APIs.
User should be able to perform conversions from `float` to/from
`Float16/BFloat16`, compare values and tests for `NaN, Inifnity, and
whether the number is denormalized.`
### Motivation and Context
User filed issues such as:
https://github.com/microsoft/onnxruntime/issues/14303
### Description
Expose `OrtValue` class API as first-class citizen.
Make it simular with C++ API.
Enable safe direct native memory access.
Make string tensor manipulation more efficient.
Avoid intermediate structures such as `NamedOnnxValue`,
`DisposableNamedOnnxvalue` and etc.
Provide more examples with `IOBinding`, although `OrtValue` API
potentially makes `IOBinding` redundant for most of scenarios, since
`OrtValue` can be created on top of any memory.
Run all the pre-trained models now with `OrtValue` API as well.
Obsolete `OrtExternalMemory class`. Obsolete IOBinding API that takes
`FixedBufferOnnxValue`.
### Motivation and Context
Make the API efficient and uniform with C++.
This aspires to address:
https://github.com/microsoft/onnxruntime/issues/14918https://github.com/microsoft/onnxruntime/issues/15381
Cc: @Craigacp
